When sneezing, the saliva droplets are arranged in a large cone shape, and a large amount of saliva droplets are displayed when they are sprayed. This dramatically illustrates the reason why you need to cover your mouth to protect others when you cough or sneeze. Credit: James Gassani

All attention is focused on COVID-19, let us not forget rhinovirus, influenza, RSV and adenovirus.

As the coronavirus takes over our news feeds and lives, you may mistakenly think that it is the only virus that currently affects humans. But it is important to remember that there are many viruses, especially respiratory viruses, that regularly infect us. These viruses range from mildly annoying viruses (such as the virus that causes the common cold) to potentially deadly viruses (such as the flu).

Despite the challenges posed by the pandemic, scientists around the world are still working hard to study these viruses to find treatments and vaccines to improve our quality of life.

Rhinovirus (from the Greek "rhino", meaning "nose") is usually associated with the common cold. They can cause nasal infections, leading to nasal congestion and runny nose. But rhinovirus has a more vicious side. They are associated with aggravation of lower respiratory diseases, such as asthma and COPD (an obstructive lung disease that causes long-term breathing problems and poor airflow).

Rhinoviruses can spread throughout the year, and there is no vaccine for them because they are an extremely diverse group of viruses. There are also no licensed antiviral drugs for rhinovirus, although scientists are working to help control diseases such as asthma and chronic obstructive pulmonary disease.

Interestingly, rhinoviruses are only found in humans and are closely related to viruses that infect our intestines.

Adenovirus was originally isolated from adenoids (the area of ​​the throat near the tonsils), hence the name. There are more than 50 human adenoviruses, most of which cause respiratory diseases. But some can cause gastrointestinal, eye (conjunctivitis) and urinary tract (cystitis) infections. In most healthy people, these viruses only cause mild, short-lived illnesses, but they tend to spread rapidly in densely populated areas.

There is no antiviral treatment for adenovirus, although some are in clinical trials). But there are two vaccines for respiratory adenovirus that can regularly break out in crowded people. These vaccines are often used by the armed forces.

An exciting area of ​​research is the use of adenovirus as an anti-cancer therapy, because certain strains can selectively infect and destroy cancer cells without affecting healthy cells.

Humans are infected with two pneumoviruses: respiratory syncytial virus (RSV) and metapneumovirus (MPV). All members of the pneumonia virus ("pneumo" means lung in Greek) are respiratory viruses, but they have a series of hosts that can infect. Like humans, certain pneumoviruses can infect cows (bovine respiratory syncytial virus), mice (mouse pneumonia virus), and birds (avian pneumovirus).

Most people will be infected with Human Respiratory Syncytial Virus (HRSV) multiple times in their lives, and more than 80% of the population will be infected at the age of two. For most healthy people, HRSV can cause a severe cold, but this will resolve on its own without any treatment. However, for people with respiratory diseases such as asthma, the consequences can be serious. In 2015 alone, RSV is estimated to have caused 3.2 million hospitalizations and more than 59,000 deaths in children under five.

HRSV is related to the development of asthma. Although this is a controversial scientific field, there are still many controversies and studies.

Parainfluenza viruses (PIV) are a subgroup of viruses called paramyxoviruses, which are closely related to other pathogens such as mumps and measles. They can also infect our respiratory tract and are the main cause of a lower respiratory tract disease called croup. People with croup often bark like seals.

Parainfluenza viruses have two different groups of paramyxoviruses, one is called respiratory viruses (PIV1 and 3) and the other is called rubella virus (PIV2 and 4). PIV1 and 3 have counterparts in other animal species, such as mice and cows, while PIV2 and 4 are relatively closely related to mumps virus.

PIV tends to spread in autumn and spring. Although researchers have made significant progress in this area, there are currently no licensed vaccines or antiviral drugs against PIV.

Considering the ability of influenza viruses to cause pandemics (such as the 1918 influenza pandemic), influenza viruses may be the most worrying respiratory virus. They are highly diverse viruses with four main types (A, B, C, and D). Except for influenza D viruses, all viruses can infect humans. Types A and B can cause severe lower respiratory tract disease and even death. Type B and Type C influenza viruses are still related to humans, while Type A influenza virus is actually a water bird virus, although Type A influenza virus spreads in humans, pigs and even bats.

Sometimes, avian influenza A virus spreads to humans across species, and may even spread well, and may cause a pandemic.

Influenza viruses continue to spread among humans because they can mutate and evade our immune response. We have vaccines for influenza viruses, but they must be updated every year to keep up with mutations.

Antiviral drugs, such as Tamiflu, if used as early as possible, can effectively reduce the time you are sick. Researchers are continuing to develop broader, longer-lasting flu vaccines and more effective antiviral drugs.

All the above respiratory viruses usually infect humans. Most people lack vaccines and effective treatments—many people disproportionately affect the most vulnerable people in society. Now that scientific and public awareness of respiratory infections has increased, we must now take advantage of this opportunity to make significant progress in respiratory infections through research and strengthening of preventive measures such as hand hygiene and social distancing.

Connor Bamford is a virology researcher at Queen's University Belfast. Connor is a virologist with more than ten years of experience in studying how the immune system protects humans and other animals from pathogenic microorganisms such as hepatitis C virus, influenza virus and Zika virus. Connor recently moved to Queen's University Belfast as the "Wellcome Trust Institution Strategic Support Fund (ISSF) Early Career Researcher" to continue his research on the human immune system and the antiviral protein called "interferon." Connor received his PhD in molecular virology from mumps virus in 2014, and then did postdoctoral research at the MRC-University of Glasgow Virus Research Center (CVR) in Scotland, UK.

Grace C Roberts is a virology researcher at Queen's University Belfast. Grace is a postdoctoral researcher in the School of Molecular and Cell Biology at the University of Leeds. Her current research focuses on the hepatitis C virus. Previously, Grace worked as a postdoc at Queen's University Belfast, researching respiratory viruses. Grace received her Ph.D. from the University of Leeds in 2019, studying chikungunya virus and its interaction with host cell immune pathways. Grace's virology experience includes working with mosquito-borne viruses (such as Chikungunya virus), hepatitis C virus, and adenovirus.

This article is provided by The Conversation.

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